Industrial wastewater is produced as a by-product of industrial processes, for example, processes in oil refineries and petrochemical plants.
Wastewater from refineries may be highly contaminated given the number of sources it can come into contact with during the refinery process. This contaminated water may, for example, be process wastewater from desalting, water from cooling towers, storm water, distillation, or cracking. This water can be recycled through many stages during the refining process and typically goes through several treatment processes, including wastewater treatment, before being released into surface water.
Existing technologies for the treatment of contaminated water in oil refineries and petrochemical plants consist of a series of sequential steps, including the steps shown in the flow diagram of FIG. 1.
To-date, the majority of the wastewater treatment is done by using the “activated sludge” (depicted in the flow diagram of FIG. 2) or “membrane bioreactors” (“MBR”) (depicted in the flow diagram of FIG. 3) technologies. In general, in activated sludge plants, atmospheric air or pure oxygen is bubbled through wastewater combined with organisms, to develop a biological floc which reduces the organic content of the wastewater. In all activated sludge plants, once the industrial wastewater has received sufficient treatment, an additional step of settling out the biological floc is required. Part of the settled material, the sludge, is returned to the system to re-seed the new industrial wastewater entering the tank. The remaining sludge then needs to be disposed of. The MBR technology combines the use of an activated sludge bioreactor with a cross flow membrane filtration loop. The membrane is used for the additional step of biological floc removal, by filtration, and as a result recycled and waste sludge are produced.
U.S. Pat. No. 6,916,427 to Roth discloses a method of purifying wastewater, including running the wastewater as a fluent into a headworks where some preliminary treatment takes place, passing the fluent into a primary reservoir where it is analyzed as to certain control parameters such as pH, dissolved oxygen and/or dissolved solids. Thereafter the fluent flows into a primary reactor having a plurality of electrolytic cells therein. While in that reactor the fluent is subjected to electrical contacts which are located at the bottom and the top of the reactor. The effluent from the primary reactor passes through a ratio weir into a secondary receptor containing sensors for the measurement of control parameters such as pH, DO, TDS and chlorine. Thereafter, the fluent is passed to a filtering device.
U.S. Pat. No. 5,989,428 to Goronszy provides a method and apparatus for treating waste material to remove selected components form the waste is described using a reactor or a series of reactors in fluid communication with each other for receiving the waste to be treated as influent. The influent forms a biomass including the waste and microorganisms and is treated by controlling the metabolic activity of the microorganisms by monitoring the oxygen utilization rate or the potential oxygen utilization rate of the biomass so as to determine the required amount of oxygen to be supplied to the biomass and to determine the period of aeration of the biomass in order to maintain a predetermined oxygen utilization rate or value so as to remove the selected components of the waste. The preferred selected components to be removed are nitrogenous, carbonaceous and/or biological phosphorus containing materials or derivatives.
US Published Patent Application No. 20080047903 to Morse discloses a system and process for optimizing chemical additions, mixing energy, mixing time, and other variables while treating a contaminated liquid stream. Samples from the contaminated liquid stream are tested to determine the optimal parameter for each variable, including type and amount of the chemicals to be added, chemical sequence, mixing energy, mixing time, temperature, and pressurization. A system of mixers, a flotation chamber, and a dewatering subsystem are designed to achieve optimal turbidity of the wastewater stream. The system can be modified in real-time in response to a continually changing contaminated liquid stream via a controller and set of sensors, valves, and ports. The process takes place during the pre-treatment stage. There is need for a stable, efficient, continuous and cost-effective wastewater treatment process to overcome the shortcomings of existing processes.